Cushion construction for air cylinders



Oct. 4, 1955 J. R. ELDER 2,719,510

CUSHION CONSTRUCTION FOR AIR CYLINDERS Filed July 21, 1951 2 SheetsSheet l INVENTOR BY J. QEX ELDER MMXFTB Oct. 4, 1955 J. R. ELDER CUSHION CONSTRUCTION FOR AIR CYLINDERS 2 Sheets-Sheet 2 Filed July 21, 1951 J. QEX ELDER l l MWW ATTORNEY United States Patent CUSHION CONSTRUCTION FOR AIR CYLINDERS Joseph Rex Elder, Jackson, Micl1., assignor to The Tomkin-Johnson Company, Jackson, Mich, a corporation of Michigan Application July 21, 1951, Serial No. 237,876

2 Claims. (Cl. 12138) The present invention relates to improvements in construction for cushioning the movement of reciprocated pistons actuated by elastic fluid such as air.

As a reciprocated piston approaches the end of its stroke within its cylinder it is often desirable to arrest the movement of the piston with a cushioning action. Coil springs have been employed within the cylinder for such a purpose. It has also been proposed heretofore to employ structure movable with the piston which would restrict the flow of air moving ahead of the piston as it approached the end of its travel to build up an air cushion. The present invention is an improvement over this latter type of structure.

It is an object of the invention to provide piston cushioning structure which avoids the necessity of close manufacturing tolerances as to the relative diameter of telescoping parts as well as the degree of concentricity that is maintained between the parts making up the assembly.

Another object is to provide an improved steel for producing an air cushion ahead of a piston as it approaches the end of its stroke.

Another object of the invention is to provide a structure of the type described in which means are provided for reducing the energy required to move the piston in the opposite direction following the cushioning action.

These and other objects and advantages residing in the specific construction, arrangement and combination of parts will more fully appear from a consideration of the following specification and the appended claims.

5 In the drawings, wherein several forms of the invention are illustrated:

Fig. I is a vertical cross-sectional view through a cylinder embodying the principles of the present invention in one of its forms,

Fig. II is a fragmentary cross-sectional view through a cylinder assembly illustrating another form of the invention,

Fig. III is a view similar to Fig. II showing a slightly different form of sealing structure from that illustrated in Fig. II,

Fig. IV is a view similar to Fig. II of another form of the invention, and

Fig. V is an enlarged cross-sectional view of the sealing member employed in the assembly of Fig. I.

In the form of the invention of Fig. I, the air cylinder has heads 12 attached at opposite ends in any suitable manner. The piston 14 is supported for reciprocation in the cylinder 10 and actuates the piston rod 16 connected thereto. On opposite sides of the piston 14 are cylindrical sealing plugs 18 and 20. A nut 22 holds the plugs 18 and and piston 14 assembled on the rod 16.

To alternately direct air under pressure against opposite sides of the piston 14 any suitable conduit (not shown) connects the inlet ports 24 and the exhaust ports 26 through a suitable four-way valve, or other suitable structure (not shown) with a source of air pressure and the atmosphere. Central ports 28 in the heads 12 are counterbored at 30 to receive sealing rings 32 with a press 2,7 19,5 1 0 Patented Oct. 4, 1955 ICC fit. As more clearly shown in Fig. V, the sealing rings 32 comprise an annular metal casing 34, an annular sealing member 35 and an annular retainer ring 40 which holds the parts assembled through the inturned flange 42.

The sealing member 35 is preferably of rubber-like material, either natural or synthetic, with a thin lip 36 being readily deformable yet substantially reinforced by the comb spring 38. In practice, it has been found that the sealing rings 32 taken the form and construction of a well known commercial oil seal ring sold under the trade name Garlock Klozure.

The nose end of the sealing plugs 18 and 20 are preferably slightly tapered at 40 to assist in leading the plugs 18 and 20 into the lips 36 of the sealing rings 32 as the piston approaches the end of its stroke, as shown in dotted outline in Fig. I. With this arrangement a reasonable amount of excentricity may exist between the cylinder 10, piston 14, plugs 18 and 20 and counterbores 30 without detrimental effect upon the sealing engagement between the plugs 18 and 20 and the rings 32. This is for the reason that the lips 36 are are capable of a limited amount of transverse adjustment in order to receive the plugs 18 and 20 if necessary because of lack of concentricity of the assembled parts.

When air pressure is fitted to the left hand head of Fig. I, the check ball valve 44 is forced from its seat. At the same time some air may flow between the plug 20 and the lips 36 of the sealing member 32. Air thus directed into the cylinder 10 against the left end of the piston 14 will move the same to the right withdrawing the plug 20 from its telescoping relationship with the sealing member 32. When this takes place the airmay flow, without restriction, into the cylinder 10 through the port 28.

As the right end of the piston 14 approaches the end of its stroke, when in the dotted line position shown in Fig. I, a seal is established between the sealing member 32 and the plug 18. This interrupts the exhausting of air ahead of the piston 14 through the port 28 and the pressure of the air trapped is increased to urge the lip 36 into firm sealing relationship with the p1ug 18 due to the inclined area of the lip which is subjected to the pressure. In this manner an air cushion is provided between one end of the piston 14 and the head 12. When the piston 14 is moved from right to left in the cylinder 10, the plug 20 telescopes with the. sealing member 32 to provide an air cushion at the opposite end of the piston in the manner just described with reference to the plug 18.

Another form of the invention is shown in Fig. 11 wherein the cylinder 46, head 48 and piston 50 assembly has a flexible annular sealing member 52' carried on the piston rod 54. Air is admitted and exhausted from the cylinder 46 through the major portion of the movement of the piston 50 through the port 56. However, as the piston 50 approaches the end of its stroke, the sealing member 52 enters the port 56 and plugs the annular clearance 58 around the rod 54 to provide an air cushion between the right-hand end of the piston 50 as viewed in Fig. II and the head 48. A needle valve 60, or other suitable valve structure, is shown regulating the flow of air in the passage 62 to regulate the air cushion. From the cross-section of the flexible sealing member 52 it will be appreciated that it will seal against air pressure from the cylinder side only. When air pressure is directed into the cylinder 46 to move the piston 50 to the left, as viewed in Fig. II, the air will flow through the port 56 past the sealing member 52. A regulated amount of air will also flow past the valve 60. After the piston 50 has suificiently moved to the left to withdraw the member 52 from the port 56, the air flow in the cylinder 46 is thereafter substantially unrestricted and is through the port 56.

Fig. III shows the arrangement of Fig. II with a slightly different torm"of fle'x'ibles'ealing member 64. Otherwise, the structure is the same as disclosed in Fig. II.

In Fig. IV is shown a modified form of structure which is similar in most respects .to that form of Fig. II (correspondingparts being designated by "snn'ilar'prime referenceeha'rac'te'rs) but which requires a greater degree (if eonc'entricity of "associated parts in its manufacture. Asrshownythe 'port"56 "-isxprovi'ded with a press fitted annular liner 66 with which the "cylinder plug portion 68 telescopes with a relatively c los'efi't as the piston approaches the end 'o'f'the stroke to provide the cylinder. Being "non-flexible, "the plug "68 seals the port 56 with the "same'effeetiveness regardless of the direction of the air ressure. Forthis-reason, "a (ih'eek valve '50 maybe provided to direct .air pressure "into the cylinder 46' to movethepistonfiil' toth'e left until the plug "68 clears the port 56 and Tthe entering air may thereafter flow st bsta'ntially unrestricted 'throu'g h'th'e annular clearance 5 f.

Havin'gth'us described my invention, what I claim as new-and desire to' protect by Letters Patent is:

"l. A'piston and cylinder assembly having an air cushion comprising afcylinde'r, a piston disposed in said cylinder for reciprocation by differential air pressure upon opposite sides "(if said piston, a 'head closing one end of said cylinder, ae'oinbina'tion-air inlet and air exhaust port defined in said head 'a'nd'lo'cated therein substantially con centric with saidcylinder for exhausting air moving ahead of said pi's't'o'n'upon its initial movement toward said head and for the inlet'ofair into said cylinder upon movement from 'said head, .a cylindrical vportion substantially concentric"with said piston and'cylinder and carried by said piston-and disposed to the side of-said piston adjacent saidhead, said cylindrical portionbeing of substantially lesser axial extent than the stroke of said piston and telescoping withsaid port as said piston approaches the end of its stroke, an annular sealing member for said port mounted on saidhead-substantially concentricto said port and having a thin flexible lip portion for engaging with said cylindricalpor'tion with a sliding seal to provide an air cushion between said .piston and saidhead as said piston approaches the end of its stroke, the flexible construction of said lip portion providing for lateral adjustment of 's'aidlip portion with respect to said cylindrical portion "to compensate 'for any slight eccentricity that might exist'between'the telescoping cylindricalportion and port, said flexible-lipportion-extending toward said piston 80 as tobe urgedinto sealing relationship with said cylindrical portion, said flexible lip portion upon movement of its-sealing engagement with said cylindrical "portion'bythe air entering said port.

2. A piston and cylinder assembly having an air cushion comprising a cylinder, a piston disposed in said cylinder for reciprocation by differential air pressure upon opposite sides of said piston, a head element closing one end of said cylinder, at cornbinationair inlet and air exhaust ort defined in said head element and'located therein substantiallyconcentric with said cylinder for exhausting'air moving alread of said piston upon its initial-movement toward said head element and for the inlet of air into said cylinder upon movement fromsaid head element, a cylindrical element substantially concentric with said piston and cylinder and carried by said piston and disposed to the side of said piston adjacent said head element, said cylindrical element being of substantially lesser axial extent than the stroke of said piston and telescoping into said port as said piston approaches the end of its stroke, an annular sealing member for said port mounted on one of said elements substantially concentric to said port and having a'thinfiexibleflip portion for engaging withsaid other element with a'sliding seal to provide an air cushion between said piston and said head element as said piston approaches the end of its stroke, the flexible construction of said 'lip portion providing for lateral adjustment of said lip portion with respect to said other'element to compensate for anyslight eccentricity that might exist betweenthe telescoping cylindrica'l element and ,port, said flexible'lip portion extending toward said piston so as to be urged into sealingrelationship with said other element, said flexiblelip ,portion upon movement of said piston from said head element being radially displaced 'from its sealing engagement with said other element by the air entering saidgport.

References Cited in the file ofthis patent UNITED STATES PATENTS 271,003 Tucker Ian. '23, 1 883 845,827 Steedman- MarfS, 1907 1,760,052 Forman May 27, 1930 1,799,366 -Heinkel Apr. 7, 1931 2,493,602 Sterrett Jan. 3, 1-950 2,547,175 Sacchini Apr. '3, 1-95 1 FOREIGN PATENTS 623,478 Great-Britain May 18, 1-949 635,950 :Great Britain Apr. 19, 1950 

